Carousel is not working in IE9 and below.

[redfrost]

Sometimes Bootstrap Carousel is not working well in IE9 and below.
You need to find carousel related code in bootstrap.js and replace with this:

!function ( $ ) {

  "use strict"

 /* CAROUSEL CLASS DEFINITION
  * ========================= */

  var Carousel = function (element, options) {
    this.$element = $(element)
    this.options = options
    this.options.slide && this.slide(this.options.slide)
    this.options.pause == 'hover' && this.$element
      .on('mouseenter', $.proxy(this.pause, this))
      .on('mouseleave', $.proxy(this.cycle, this))
  }

  Carousel.prototype = {

    cycle: function () {
      this.options.interval
        && (this.interval = setInterval($.proxy(this.next, this), this.options.interval))
      return this
    }

  , to: function (pos) {
      var $active = this.$element.find('.active')
        , children = $active.parent().children()
        , activePos = children.index($active)
        , that = this

      if (pos > (children.length - 1) || pos < 0) return

      if (this.sliding) {
        return this.$element.one('slid', function () {
          that.to(pos)
        })
      }

      if (activePos == pos) {
        return this.pause().cycle()
      }

      return this.slide(pos > activePos ? 'next' : 'prev', $(children[pos]))
    }

  , pause: function () {
      clearInterval(this.interval)
      this.interval = null
      return this
    }

  , next: function () {
      if (this.sliding) return
      return this.slide('next')
    }

  , prev: function () {
      if (this.sliding) return
      return this.slide('prev')
    }

  , slide: function (type, next) {
      if(!$.support.transition && this.$element.hasClass('slide')) {
        this.$element.find('.item').stop(true, true); //Finish animation and jump to end.
      }
      var $active = this.$element.find('.active')
        , $next = next || $active[type]()
        , isCycling = this.interval
        , direction = type == 'next' ? 'left' : 'right'
        , fallback  = type == 'next' ? 'first' : 'last'
        , that = this
        , e = $.Event('slide')

      this.sliding = true

      isCycling && this.pause()

      $next = $next.length ? $next : this.$element.find('.item')[fallback]()

      if ($next.hasClass('active')) return

      if ($.support.transition && this.$element.hasClass('slide')) {
        this.$element.trigger(e)
        if (e.isDefaultPrevented()) return
        $next.addClass(type)
        $next[0].offsetWidth // force reflow
        $active.addClass(direction)
        $next.addClass(direction)
        this.$element.one($.support.transition.end, function () {
          $next.removeClass([type, direction].join(' ')).addClass('active')
          $active.removeClass(['active', direction].join(' '))
          that.sliding = false
          setTimeout(function () { that.$element.trigger('slid') }, 0)
        })
      }else if(!$.support.transition && this.$element.hasClass('slide')) {
        this.$element.trigger(e)
        if (e.isDefaultPrevented()) return
        $active.animate({left: (direction == 'right' ? '100%' : '-100%')}, 600, function(){
            $active.removeClass('active')
            that.sliding = false
            setTimeout(function () { that.$element.trigger('slid') }, 0)
        })
        $next.addClass(type).css({left: (direction == 'right' ? '-100%' : '100%')}).animate({left: '0'}, 600,  function(){
            $next.removeClass(type).addClass('active')
        })
      } else {
        this.$element.trigger(e)
        if (e.isDefaultPrevented()) return
        $active.removeClass('active')
        $next.addClass('active')
        this.sliding = false
        this.$element.trigger('slid')
      }

      isCycling && this.cycle()

      return this
    }

  }


 /* CAROUSEL PLUGIN DEFINITION
  * ========================== */

  $.fn.carousel = function ( option ) {
    return this.each(function () {
      var $this = $(this)
        , data = $this.data('carousel')
        , options = $.extend({}, $.fn.carousel.defaults, typeof option == 'object' && option)
      if (!data) $this.data('carousel', (data = new Carousel(this, options)))
      if (typeof option == 'number') data.to(option)
      else if (typeof option == 'string' || (option = options.slide)) data[option]()
      else if (options.interval) data.cycle()
    })
  }

  $.fn.carousel.defaults = {
    interval: 5000
  , pause: 'hover'
  }

  $.fn.carousel.Constructor = Carousel


 /* CAROUSEL DATA-API
  * ================= */

  $(function () {
    $('body').on('click.carousel.data-api', '[data-slide]', function ( e ) {
      var $this = $(this), href
        , $target = $($this.attr('data-target') || (href = $this.attr('href')) && href.replace(/.*(?=#[^\s]+$)/, '')) //strip for ie7
        , options = !$target.data('modal') && $.extend({}, $target.data(), $this.data())
      $target.carousel(options)
      e.preventDefault()
    })
  })

}( window.jQuery );

[redfrost]

Or download this patched file and rename.

Bootstrap 2.3 custom Carousel patched for IE
https://raw.github.com/redfrost/Bootstrap-Collection/master/2.3/js/script-carousel-ie.js